Houthi rebels on Saturday allegedly abducted a Yemeni activist in the capital Sana'a after his participation in a rally to call for the expulsion of the group from the city, eyewitnesses said.

Activist Shadi Khasrouf was kidnapped by Houthis near a military zone in Sana'a and transferred to an undisclosed location, an eyewitness told Anadolu Agency.

"The militants assaulted several protestors and fired shots into the air," the witness said.

Houthi leaders could not be immediately reached for comment.

Earlier Saturday, dozens of Yemenis staged a demonstration in central Sana'a to demand the expulsion of Houthis from the capital and other Yemeni provinces.

This week, the group has tightened its grip on the capital, storming government buildings, including a state-run oil and gas company and the state television and radio headquarters.

Houthis also broke into the offices of Ath-Thawra newspaper, demanding the dismissal of its board chairman. 

On Wednesday, Yemeni Prime Minister Khaled Bahah suggested that his government may resign, exasperated with the Houthis campaign, according to Reuters.

Since they took control of Sana'a in late September, the Houthis have sought to expand their influence to other parts of the country as well.

The Houthis' growing strength in fractious Yemen has raised fears of sectarian conflict in the country, which has remained in turmoil since a 2011 popular uprising ended the decades-long rule of president Ali Abdullah Saleh one year later.